To solve this problem, we need to identify where cuboidal epithelium with a brush border of microvilli is found. Let's analyze each option:$\newline \bullet$Option 1: Ducts of salivary glands$\newline$ - The ducts of salivary glands are typically lined with simple cuboidal or columnar epithelium, but they do not have a brush border of microvilli.$\newline \bullet$Option 2: Proximal convoluted tubule of nephron$\newline$ - The proximal convoluted tubule (PCT) of the nephron is lined with simple cuboidal epithelium that has a brush border of microvilli.$\newline$ - This brush border increases the surface area for reabsorption, which is a key function of the PCT.$\newline \bullet$Option 3: Eustachian tube$\newline$ - The Eustachian tube is lined with ciliated columnar epithelium, not cuboidal epithelium with a brush border.$\newline \bullet$Option 4: Lining of intestine$\newline$ - The lining of the intestine is composed of simple columnar epithelium with microvilli, not cuboidal epithelium.$\newline$Based on the analysis, the correct answer is Option 2: Proximal convoluted tubule of nephron.